STATEN ISLAND, N.Y. -- Little Christopher Harris could live to be 100, but the early Christmas gift he received today will surely be the best one he ever gets.

Christopher’s surprise present wasn’t an Xbox, computer or toy. It was something much better: The safe return home of his mother, Chief Warrant Officer 2 Karyn Obey, from her third tour of duty with the U.S. Army in Afghanistan.

The tearful mother and wide-eyed son were reunited amid the gasps and cheers of Christopher’s third-grade classmates at PS 54, Willowbrook. Separated for six months, they hugged each other like they’d never let go.

"I just wanted to give him a little something special for Christmas," said Ms. Obey, 34, who’s been stationed since July on her latest stint in Afghanistan. "He knew I was coming home. He didn’t know when."

Eight-year-old Christopher was lost for words at first, burying his head in his mother’s arms.

But he beamed as his schoolmates shouted out "Happy holidays" in unison to him and his family. His grandparents, Cheryl and Arnold Obey, with whom he lives in Meiers Corners, and Ms. Obey’s sister, Tonya, also joined the reunion, which they helped plan with school administrators.

"It’s wonderful. It’s a great Christmas present," said Arnold Obey, who is retired as a principal at PS 31, New Brighton. His wife is retired as assistant principal at Prall Intermediate School, West Brighton.

Principal Karen LaRosa said Christopher is proud of his mom, a 10-year Army veteran stationed at Fort Lewis in Tacoma, Wash., and often talks about her. And with his grandparents as former educators, the reunion at school was a natural choice.

"We wanted to have this experience in the classroom," she said.

Ms. Obey flew in late yesterday and spent the night at her sister’s New Jersey home. She wore her Army camouflage fatigues today.

And it was a homecoming in more than one way: Cheryl Obey is a PS 54 alumna.

For Christopher’s classmates, the mother-and-child reunion was a lesson in life and love.

Ms. Obey and Christopher took chairs in the center of teacher Kathy Ruggiero’s classroom as the children sat around them. Christopher nestled his head in his mother’s arm, grinning and occasionally mugging it up as she answered the students’ questions for more than 20 minutes.

Ms. Obey told them she joined the Army because she needed a good job and wanted to see the world, that her accommodations in Afghanistan are better than one might expect, and that our military personnel isn’t just hunting for bad guys in that country. They’re also building roads and helping the populace get needed medical attention.

She said the Army is much like school — a lot of rules and people telling you what to do — but she likes it.

Besides Afghanistan, she’s been deployed to Kuwait, Uzbekistan and several European countries, including Germany, where Christopher was born.

The class listed raptly, oohing and aahing when Ms. Obey told them singer Jordin Sparks had visited her unit. They groaned only once — when she said she had never handled an AK-47 rifle.

"We wanted to make it more real," Assistant Principal Elizabeth Hession said of the decision to hold the reunion at school and have the children speak to an active military service member. "It’s something that’s happening in our community."

Ms. Obey said she and Christopher will spend the next two weeks relaxing and hanging out with family and friends.

She heads back to Afghanistan on Jan. 6 for another six-month tour, she said.

Back overseas, she’ll keep in touch with Christopher on a nearly daily basis through Skype and the telephone. But those electronic communications can’t replace an experience like today.